Heretofore, various techniques have been adopted for specifying the position of any bright point, dark point, bright line or dark line which is the improper part of a liquid crystal panel.
As an example, the simplest technique is a technique wherein dimensions from the ends of a screen to the improper part are measured on the screen, and the address values of the improper part are specified by comparing the resulting measured values with the values of an address conversion table prepared beforehand. Since this technique does not require any special contrivance for specifying the improper part, it is advantageous in cost. The technique, however, has had the problem that accurate address values are not always obtained on account of dimensional measurement errors, etc.
On the other hand, there has been employed a technique wherein, as shown in FIG. 5, a cross-cursor screen in which one vertical line and one horizontal line intersect in the shape of a cross and which displays the coordinate values of an intersection point is displayed on the screen of the liquid crystal panel. More specifically, the address values of the improper part (crosspoint) are read from the screen in such a way that the vertical line and/or horizontal line of a cross cursor are/is moved every pixel (every dot) by appropriately manipulating upper, lower, left and right manipulation keys, until the intersection point (crosspoint) is superposed on the improper part.
The function of displaying such a cross-cursor screen is a function which is already incorporated in a pattern generator commercially available. This function, however, is very expensive and is unsuitable for reduction in cost.
Meanwhile, an OSD (on-screen display) circuit for presenting various displays is mounted in the liquid-crystal television set or the like. When the OSD circuit is used, information for enhancing a display quality can be offered by adjusting parameters, for example, contrast, brightness, sizes in vertical/horizontal directions, and a geometrical shape. A configurational example of the OSD circuit for offering such information is disclosed in, for example, JP-A-2002-140061.
Also, there has been proposed an image display apparatus wherein, in case of testing the defects or the likes of the liquid crystal panel, the set values of registers in a control circuit are altered, whereby a test pattern to be displayed is altered (refer to, for example, JP-A-11-272222). Concretely, seven registers AAA-GGG are employed. By way of example, when the set value of the register AAA is altered from “000” to “055”, the set value of the register DDD from “005” to “042”, and the set value of the register FFF from “033” to “063”, the display is altered from a standard pattern to any desired test pattern. In this case, the set values of the registers are altered by control signals stored in the memory of a microcomputer beforehand, thereby to omit the labor of individually setting and altering the values of the registers. Besides, the test pattern is created by utilizing a pattern generator function which the control circuit has.